1

Characterize a Habitable Planet

SAG-4 WHAT to measure

with WHAT accuracy ?

Lisa Kaltenegger, MPIA/HarvardEXO-PAG mtg, Jan. 9, 2011

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SAG 4: Science: modeling ()1) derive accuracy of parameters needed to characterize

- Earth (HZ)- Super-Earth (HZ)

2) use “standard” models (Earth and Super-Earth)- to compare models of different groups- generate "standard" spectra as input for designs- to compare models of different goups

3) deliverables: - report on spectral features (Earth & Super-Earth)

- report on parameter accuracy needed () - spectra as input for studies & e.g. SAG 7 & 8

KICK-off – collaboration of modeling teams & lively discussion

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The IDEA: Line of Evidence

FIND

INTERIOR

ATMOSPHERE

LIFE ?

SPECTRAL FINGERPRINT

WHAT KIND

FORMATION

Density ?

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MODEL

STAR: FluxPLANET: Composition

OutgassingTectonicGeoch. CycleMagnetosphere

Re-radiation

= ATMOSPHERES

SPECTRAL Fingerprint

DATA

SAG 4: 1) derive accuracy to characterize- Earth (HZ)- Super-Earth (HZ)

2) define “standard” models - to compare models

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Atmosphericescape

OutgassingEarly or continuous

Geochemical recyclinge. g. carbonate silicate cycle

Biological processing

photochemistry

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RV & Transits: density

Torres 2008

Fortney, 2007Sasselov 2007

Zeng & Sasselov (2010), Valencia et al. 2010, Sotin et al. 2010,

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Transit Geometryz

T( z, )

h is the effective height of an opaque

atmosphere:

h() = ∫ (1-T) dz

SoR() = R0 + h()

h ≈ T/(g )

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Explore Planets - EGP

Atmosphere by transits... HD189733b (Tinetti07, Swain08)Earth (Palle 09, Kaltenegger 09)

2007 +

Water in HD 189733b

Tinetti et al. (2007)

GJ 1214 - Spectrum

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NOT Earth-like (R, M)Not a CLEAR H/He atm (spectrum)

Bean et al nature 2010

11Kaltenegger & Traub ApJ 2009Palle et al. Nature 2009Data: ATMOS B. Irion 2002

Earth Primary Transit: collect transmitted starlight

SNR = N1/2(tot) * 2Rp h / Rs2

2002/2014+ ?

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Habitable Planets with transits = Easy

13NEXT STEP

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The TEST =observationsThe Pale Blue Dot Voyager image, 4 bil. km

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Signs Of Life On An Earth-like Planet

Vegetation ?

Plantproduct

Surface features e.g.Plantlife

Bacteria

observed

WaterOxygen Carbon

dioxide

Methane

Nitrousoxide

Ozone

Needed for life

Primordial; & bacteria product

Adapted from Traub

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Signs Of Life On An Earth-like Planet

Vegetation – good enough SNR per 1/20 of planet‘s rotation to detect surface feature

Water makes Oxygen – WITHOUT life

Oxygen

Carbon dioxide - greenhouse & HZ extend

& Methane (or other reducing gas) Biomarker

Nitrous oxide

Ozone

17Direct imaging

Direct Imaging & Secondary Eclipse

~ Rpl2

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Visible spectrum of Earth

Observed Earthshine, reflected from dark side of moon.Ref.: Kaltenegger et al 2007, ApJ 574, 2007

see also e.g.: Montanez-Rodrigez 2005, 07, Arnold 2002, 06, 09; Turnbull 06

Rayleigh

Ozone O3

Chlorophyll ?

Oxygen O2

Water H2O

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VIS & near-IR: Reflected light

Meadows et al 2006

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Kaltenegger, Traub Jucks 2007 ApJ

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flux

at 1

0 pc

(ph

oton

s m

-2 h

r-1

m-1)

wavelength (m) Selsis 08, Tinetti 2007

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Earth IR-emission

Kaltenegger, Traub, Jucks 2007 (ApJ)

TES data; Christensen 2004

23Selsis 2007 (model Tinetti)

Features: 1) observables & 2) unique ?

24Kaltenegger et al 2007 ApJmid IR (5-20m): Res = 25

Different evolution state / age / mass / etc.

THE TEST: GRID of Spectra of different planets – Exoplore underlying physics- Unique?- Detectable?- Inst. requirements- Retrieval from data?

26Udry et al 2007, Selsis et al 2007, van Braun et al 2007, vanParis et al, Kaltenegger et al, ....

Gl 581d spectra& star/planet contrast ratioKaltenegger, Mohanty & Segura ApJ 2011

Spectra (0.1 - 100 m): Resolution 15027

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WHY ?

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Summary• Models: - WHAT to measure HOW WELL

- to explore the underlying physics- to have compelling diversity

- predict spectra & characterize ()- instrument design, data analysis ()

• Earth: a rosetta stone for exoplanets

WELCOME TO THE TEAM !!!

e-mail: lkaltene@cfa.harvard.edu

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TEST: explosive exovolcanos ? Res = 150, SNR calc. for JWST (pure photon noise, template input for instruments)

Kaltenegger & Sasselov (ApJ 09), Kaltenegger & Henning (ApJ 2010)

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DETAILS: Albedos & Clouds

Kaltenegger 07

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Clouds VIS = bright!: Earth avg 60%

IR

Kaltenegger 07

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Selsis et al, Paille et al, Kaltenegger et al

Distinguishing atm & planet comp

34Miller-ricci et al 2008

h ≈ T/(g )

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Earth: ATMOS-3:Transmission validation in far-IR

ATMOS-3 transmission of sunlight through Earth’s atmosphere, measured with a fast FTS on Shuttle

yellow = model

Fit is close, but line wings are not perfect, perhaps owing to line-mixing effects in strong bands.

Note low transmission below 10 km.

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Ray-by-ray spectra, visible & near-infrared

Short wavelength range of transmission spectrum.

Note:-strong O3 bands

- at 0.3 & 0.6 μm,- weak H2O bands, - strong Rayleigh in blue,- low transmission < 10 km.

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Mini-Neptunes

Super-Earths

8 - 15 ME

CharacteristicsMASS – tectonic, needed ?RADIUS – - INTERIOR vs ATMTEMPERATURE – Eff vs. surfaceALBEDO - pattern? clouds, surface)